Display Apparatus Capable of Image Scanning and Driving Method Thereof

ABSTRACT

According to an embodiment of the present invention, a display apparatus capable of image scanning and a method for driving the same are provided. 
     According to an embodiment of the present invention, a display apparatus capable of image scanning is provided including a contact sensor arranged in each unit pixel. The contact sensor includes a pixel electrode forming a contact capacitance by contact with a contact means; a reset transistor where a drain electrode is connected to a node where the contact capacitance is formed, and each of a gate electrode and a source electrode is connected to a first scan line to which a selective signal is applied; an amplifying transistor where a gate electrode is connected to the drain electrode of the reset transistor, and a source electrode is connected to a power input terminal; and a detecting transistor where a drain electrode is connected to the drain electrode of the amplifying transistor, a gate electrode is connected to a second scan line to which a selective signal is applied, and a source electrode is connected to a readout line detecting a current corresponding to the contact capacitance.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119 of KoreanApplication Nos. 10-2014-0156873, filed on Nov. 12, 2014,10-2014-0190692, filed on Dec. 26, 2014, and 10-2015-0044067, filed onMar. 30, 2015 which are hereby incorporated by reference in theirentirety.

BACKGROUND

1. Technical field

The present invention relates to a display apparatus capable of imagescanning and a driving method thereof. More specifically, the presentinvention relates to a display apparatus capable of image scanning withan aperture ratio improved than the conventional one and a drivingmethod thereof.

2. Related Arts

A touchscreen panel is a device for inputting user command by touchingletters or diagrams displayed on the screen of an image display devicewith a human finger or other touch means, and is used attached to animage display device. The touchscreen panel converts the touch locationtouched with the human finger, etc. into electrical signals. Theelectrical signal is used as an input signal.

The touchscreen panel adopts various touch detection methods such as aresistance membrane method, an optical method, a capacitive method, anultrasonic wave method, etc. According to the capacitive method, thetouchscreen panel detects whether a touch is made using the capacitancechanging when a touch generating means contacts the screen of a displayapparatus. A touchscreen panel of the capacitive method may detectcontact by a human finger, a conductive touch pen, etc.

Meanwhile, recently, as security matters are becoming an issue, securityissues relating to personal portable devices such as smartphones, tabletPCs, etc. are on the rise. As portable devices are being used morefrequently, security is a requisite for e-commerce through portabledevices, and according to such needs, biometric data such asfingerprints, iris, face, voice, blood veins, etc. are used.

Among the various biometric information authentication technologies, themost commonly used technology is the authentication technology usingfingerprints. Recently, products introducing fingerprint recognition andauthentication technology using the same to smartphones and tablet PCs,etc. have been released.

However, in order to graft sensors for fingerprint recognition onportable devices, a separate device for fingerprint recognition needs tobe installed, in addition to an image display device, which makes thevolume of portable devices bigger.

Also, recently, flexible image display devices are being developed, andin this case, the touchscreen panel applied to the flexible imagedisplay device needs to be flexible as well.

Thus, it became necessary to develop a technology granting flexibility,without requiring a separate space for a fingerprint recognition sensorin the portable device, while not bothering the display area.

SUMMARY OF INVENTION

The present invention aims to solve the above problems of the relatedart. It is an object of the present invention to rapidly increase themagnitude of a signal detected in a sensor, compared with a circuitusing electric charge sharing.

It is another object of the present invention to design a contact sensorto be contained in a display unit pixel, so that an image touched on thedisplay screen is scannable at, at least a part of the displayapparatus.

It is another object of the present invention to use a transparenttransistor and enlarge the area of a pixel electrode, thereby improvingimage sensitivity of an object to be detected, and integrate a sensorcapable of image scanning in a display, thereby increasing integratedspatial efficiency in an electronic device.

According to an embodiment of the present invention for achieving thepurpose, there is provided a display apparatus capable of imagescanning, including a contact sensor arranged in each unit pixel. Thecontact sensor includes a pixel electrode forming a contact capacitanceby contact with a contact means; a reset transistor where a drainelectrode is connected to a node where the contact capacitance isformed, and each of a gate electrode and a source electrode is connectedto a first scan line to which a selective signal is applied; anamplifying transistor where a gate electrode is connected to the drainelectrode of the reset transistor, and a source electrode is connectedto a power input terminal; and a detecting transistor where a drainelectrode is connected to the drain electrode of the amplifyingtransistor, a gate electrode is connected to a second scan line to whicha selective signal is applied, and a source electrode is connected to areadout line detecting a current corresponding to the contactcapacitance.

The reset transistor, the amplifying transistor, and the detectingtransistor may be arranged so as not to overlap a unit color pixel in acolor filter layer, and the pixel electrode may be arranged to overlapat least a part of the unit color pixel.

The reset transistor may be turned on by the selective signal from thefirst scan line and deliver to the drain electrode a signal from thepower input terminal applied to the source electrode.

The amplifying transistor may generate a current varying depending on avoltage charged in the contact capacitance and deliver the generatedcurrent to the detecting transistor.

The detecting transistor may be turned on by the selective signal fromthe second scan line and deliver to the readout line the currentgenerated by the amplifying transistor.

In the sensor, the selective signal applied to the second scan line maybe applied after the selective signal is applied to the first scan line.

In the sensor, the reset transistor, the amplifying transistor, and thedetecting transistor may be formed of a transparent thin film transistorand overlap at least a part of the unit color pixel in a color filterlayer.

The display apparatus capable of image scanning may determine whethercontact is made to an upper part of the contact sensor and contactcondition, based on the current of the readout line detected after theselective signal is supplied to the first and second scan lines.

A passivation layer may be formed between the pixel electrode, and thereset transistor, the amplifying transistor and the detectingtransistor, and the pixel electrode may be connected to the drainelectrode of the reset transistor or the gate electrode of theamplifying transistor through a contactor formed through an end of thepassivation layer.

The pixel electrode may be arranged opposite a substrate in which thereset transistor, the amplifying transistor, and the detectingtransistor are arranged, and the pixel electrode may be connected to thedrain electrode of the reset transistor or the gate electrode of theamplifying transistor through a via formed through an end of thesubstrate.

The display apparatus may further include a data line, and at least apart of the reset transistor, the amplifying transistor, the detectingtransistor, the pixel electrode, and the signal line constituting eachcontact sensor of a pair of contact sensors unidirectionally arrangedare symmetrical with respect to the data line or the readout linearranged between the pair of contact sensors.

According to an embodiment of the present invention for achieving theabove objections, there is provided a display apparatus capable of imagescanning, including a sensor array layer including a contact sensorarranged in each unit pixel and a color filter layer including a unitcolor pixel. The contact sensor includes a transparent pixel electrodeforming a contact capacitance by contact with a contact means andarranged to overlap the unit color pixel; a reset transistor receiving aselective signal from a first scan line and delivering an input powersignal to the contact capacitance; an amplifying transistor generating acurrent varying depending on a voltage charged in the contactcapacitance; and a detecting transistor receiving a selective signalfrom a second scan line and detecting the current to deliver the currentto a readout line. The reset transistor, the amplifying transistor, andthe detecting transistor are arranged so as not to overlap the unitcolor pixel.

According to an embodiment of the present invention for achieving theabove objections, there is provided a method for driving a displayapparatus, including the steps of charging a contact capacitance formedbetween a pixel electrode and a contact means through a reset transistorturned on by receiving a first selective signal; generating a currentvarying depending on a voltage charged in the contact capacitancethrough an amplifying transistor; and detecting the generated currentthrough a detecting transistor turned on by receiving a second selectivesignal, to determine whether contact is made to an upper part of thecontact sensor and contact condition.

According to an embodiment of the present invention, the magnitude of asignal to be detected can increase by using a coupling phenomenonoccurring from parasitic capacitance included in transistors andperipheral circuit configurations.

Also, according to an embodiment of the present invention, a transparentelectrode can be implemented with an enlarged area, thereby allowing forvisibility and increasing image sensitivity of a display apparatus.

Also, according to an embodiment of the present invention, a sensorcapable of image scanning is integrated in the display screen, therebyincreasing integrated spatial efficiency in an electronic device.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating an image of an electronic equipmentaccording to an embodiment of the present invention;

FIGS. 2 a, 2 b, 2 c and 2 d are cross-sectional views illustrating theconstitution of a display apparatus having an image scanning functionaccording to an embodiment of the present invention;

FIG. 3 is a plan view illustrating the constitution of the displayapparatus according to an embodiment of the present invention;

FIG. 4 is a view illustrating the constitution of a sensor array layerimplementing the image scanning function according to an embodiment ofthe present invention;

FIG. 5 is a circuit diagram illustrating an exemplary embodiment of acontact sensor arranged in a sensor array;

FIG. 6 is a circuit diagram illustrating the configuration of acapacitive contact sensor applicable for a display apparatus accordingto an embodiment of the present invention;

FIGS. 7, 8, and 9 are circuit diagrams illustrating the constitution ofcapacitive contact sensors according to embodiments of the presentinvention;

FIG. 10 is a timing diagram for explaining the operation of a contactsensor according to an embodiment of the present invention;

FIG. 11 is a plan view illustrating a contact sensor according to anembodiment of the present invention;

FIG. 12 is a plan view illustrating a sensor array layer where aplurality of contact sensors are arranged, according to an embodiment ofthe present invention;

FIG. 13 is an enlarged plan view illustrating the contact sensor of aunit pixel illustrated in FIG. 12;

FIG. 14 is a side view illustrating the contact sensor of a unit pixelillustrated in FIG. 13 taken along the line A-A′;

FIG. 15 is a side view illustrating the contact sensor of a unit pixelillustrated in FIG. 13 taken along the line B-B′;

FIG. 16 is a side view illustrating the contact sensor of a unit pixelillustrated in FIG. 13 taken along the line C-C′;

FIG. 17 is a side view illustrating a contact sensor according to anembodiment of the present invention;

FIG. 18 is a plan view illustrating a sensor array layer where aplurality of contact sensors are arranged, according to an embodiment ofthe present invention;

FIG. 19 is an enlarged plan view illustrating the contact sensor of aunit pixel illustrated in FIG. 18; and

FIG. 20 is a plan view illustrating a contact sensor according to anembodiment of the present invention.

DETAILED DESCRIPTION

Hereinafter, the present invention will be explained with reference tothe accompanying drawings. The present invention, however, may bemodified in various different ways, and should not be construed aslimited to the embodiments set forth herein. Also, in order to clearlyexplain the present invention, portions that are not related to thepresent invention are omitted, and like reference numerals are used torefer to like elements throughout.

Throughout the specification, it will be understood that when an elementis referred to as being “connected to” another element, it may be“directly connected to” the other element, or intervening elements orlayers may be present. Also, it will also be understood that when acomponent “includes” an element, unless there is another oppositedescription thereto, it should be understood that the component does notexclude another element but may further include another element.

In the present specification, “contact recognition” means a functionrecognizing an object in contact with a surface, and it should beunderstood to cover recognition of fingerprint or touch by a humanfinger, or recognition of touch by other touch generating means.

Hereinafter, examples of the present invention will be explained in moredetail with reference to the accompanying drawings.

FIG. 1 is a view illustrating an image of an electronic equipmentaccording to an embodiment of the present invention.

Referring to FIG. 1, an electronic equipment 10 according to anembodiment includes a display apparatus DP.

The electronic equipment 10 may be a digital equipment includingwireless or wired communication functions or other functions. Forexample, it may be a digital equipment with operation skills including amemory means and a microprocessor, such as mobile phones, navigations,web pads, PDAs, workstations, personal computers (e.g., laptopcomputers, etc.). Smartphone will be presented as a preferable example,but electronic equipment is not necessarily limited thereto.

A display apparatus DP is formed on a surface of an electronic equipment10. Preferably, as illustrated in FIG. 1, the display apparatus may beformed on a front surface of an electronic equipment 10 and implementedas a touchscreen panel performing the function as an input device aswell.

According to an embodiment of the present invention, the displayapparatus DP may perform the function of recognizing a fingerprint, inaddition to detecting whether contact is made by a touch generatingmeans (for example, finger, etc.) and the contact location.

Specifically, when driving a first application, the display apparatus DPmay function as a touchscreen for driving a specific function, and whendriving a second application, the fingerprint recognition function maybe implemented in the fingerprint input window FP area displayed on thedisplay apparatus DP or the entire area of the display apparatus DP.

As will be described below, touch by a touch generating means or contactby a ridge and valley of a fingerprint is made by sensors consisting ofa plurality of rows and columns. In order to recognize fingerprints,contact by the ridge and contact by the valley need to be distinguishedfrom one another. Thus, the resolution of sensing contact associatedwith the number of sensors included in the display apparatus DP shouldbe formed to an extent to distinguish the contact by the ridge from thecontact by the valley of fingerprints.

FIGS. 2 a, 2 b, 2 c and 2 d are cross-sectional views illustrating theconstitution of a display apparatus having an image scanning functionaccording to an embodiment of the present invention. FIGS. 2 a, 2 b, 2 cand 2 d present a constitution integrating the image scanning functioninto a liquid crystal display (LCD) as an example.

Referring to FIGS. 2 a, 2 b, 2 c and 2 d, the LCD includes a firstsubstrate 210, a thin film transistor layer 220, a liquid crystal layer230, a color filter layer 240, a second substrate 250, and a coverwindow 260, layered in order.

The LCD is operated by a principle implementing the desired color andimage by allowing light illuminated from a back light unit (BLU) placedon the lower part of a first substrate 210 to penetrate into a liquidcrystal layer 230, and then pass through a color filter layer 240implementing colors by extracting colors in pixel units. The thin filmtransistor layer 220 has a function of delivering or controllingelectronic signals, and the liquid crystal present on the liquid crystallayer 230 controls the penetration of light by varying molecularstructure according to the applied electronic signal.

The sensor array layer 300 performing the function of detecting contactby a touch generating means or recognizing fingerprints according to anembodiment of the present invention, i.e., performing the image scanningfunction, may be arranged on a certain area of the LCD.

First, as illustrated in FIG. 2 a, the sensor array layer 300 accordingto an embodiment may be arranged in a layer adjacent the color filterlayer 240. In this case, the sensor array layer 300 may be arranged in alower area of the color filer layer 240 or in an area between a colorfilter area 240 and a second substrate 250.

Next, as illustrated in FIG. 2 b, the sensor array layer 300 accordingto an embodiment may be arranged between a second substrate 250 and acover window 260, and as illustrated in FIG. 2 c, the sensor array layermay be arranged in the upper part of the cover window 206 to protect thedisplay apparatus.

As illustrated in FIG. 2 c, when a sensor array layer 300 is arranged inthe upper part of the cover window 260, a separate protective layer 270should be formed on top of it in order to protect the sensor array layer300.

Meanwhile, as illustrated in FIG. 2 d, the sensor array layer 300according to an embodiment may be formed on the same layer as the thinfilm transistor layer 220 implemented with circuits for driving thedisplay apparatus.

In the above, an example of implementing the display apparatus as an LCDwas explained. However, it is obvious that the display apparatus may beimplemented as other types of display apparatuses such as an organiclight emitting diode (OLED) display apparatus or an electro phoreticdisplay (EPD), etc.

The OLED display apparatus may be formed in a structure having OLEDelements formed with electrode layers on both surfaces, arranged on thesubstrate. However, in this case, the sensor array layer 300 having animage scanning function according to an embodiment of the presentinvention may be formed on the upper part of the substrate or the upperpart of the OLED element, etc.

FIG. 3 is a plan view illustrating the constitution of the displayapparatus according to an embodiment of the present invention.

FIG. 3 illustrates a color filter layer 240 and a sensor array layer300. As illustrated above, the sensor array layer 300 may be formed on arelatively upper part with respect to the color filter layer 240, or onits lower part.

The sensor array including a plurality of contact sensors according toan embodiment may be formed on the front surface of the display, and maybe formed on a certain area of the display according to anotherembodiment. When the sensor array is formed on a certain area of thedisplay, an area without a contact sensor may be configured so thatthere is no step between the area and an area with a contact sensorthrough passivation (not shown).

The contact sensor SN may be implemented as a capacitive method sensorincluding a plurality of transistors.

The color filter layer 240 may be configured to include red pixels Rindicating red images, green pixels G indicating green images, and bluepixels B indicating blue images. Each one of the red pixel R, greenpixel G, and blue pixel B forms one unit pixel, and it may be explainedthat these unit pixels are formed in the form of a matrix consisting ofa plurality of rows and columns. Accordingly, one unit pixel may includeone contact sensor SN.

According to an embodiment, the contact sensor SN is formed on thesensor array layer 300, and when viewed from the top, the sensingcircuit (e.g., transistor and wirings) of the contact sensor SN isarranged in an area not overlapping the red pixel R, green pixel G andblue pixel B of the color filter layer 240, and the pixel electrode ofthe contact sensor SN may be arranged in an area overlapping at least apart of the color pixels (R, G or B) as a transparent electrode materialsuch as ITO, etc. or in a certain area not overlapping the color pixels.FIG. 3 illustrates providing a contact sensor SN at the lower part ofthe unit pixel. However, the contact sensor may be provided at the upperpart or side surface part, etc. of the unit pixel. Also, one of the redpixel R, green pixel G, and blue pixel B may be made to be relativelysmaller so as to place the sensing circuit of the contact sensor SN in acorresponding location.

According to another embodiment, when using a transparent electrodematerial for the transistor and wiring, the contact sensor SN may beformed to overlap the red pixel R, green pixel G and blue pixel B of thecolor filter layer 240 up to the sensing circuit, in addition to thepixel electrode, in the sensor array layer 300. Accordingly, since thecontact sensor SN may be formed to overlap unit pixels, the resolutionof image sensing may increase by arranging at least two contact sensorsSN for each unit pixel, and the sensitivity of image sensing may beimproved by forming the unit contact sensor SN to be larger.

FIG. 4 is a view illustrating the constitution of a sensor array layerimplementing the image scanning function according to an embodiment ofthe present invention.

Referring to FIG. 4, the sensor array layer 300 includes a plurality ofscan lines (SL1, SL2, SLn) and a plurality of readout lines (RL1, RL2,RL1). The plurality of scan lines (SL1, SL2, SLn) are provided with scansignals in order, and the plurality of readout lines (RL1, RL2, RL1)receive signals outputted from the contact sensor SN and deliver them toa circuit (not shown) which processes the signals.

According to an embodiment, the scan signal provided to the plurality ofscan lines may be provided from a scan driver of the sensor array layer300.

The scan lines (SL1, SL2, SLn) and readout lines (RL1, RL2, RL1) arearranged to intersect one another, and at least one contact sensor SNmay be formed at each intersection.

FIG. 5 is a circuit diagram illustrating an exemplary embodiment of acontact sensor SN arranged in a sensor array layer 300.

Referring to FIG. 5, the contact sensor SN may include a pixel electrode(not shown), a switch transistor T1, and a sensing transistor T2. When acontact means contacts the pixel electrode, a contact capacitance C1 maybe formed.

In FIG. 5(a), a gate electrode and a drain electrode of the switchtransistor T1 are connected to a first scan line SL1, and a sourceelectrode is connected to a node where the contact capacitance C1 isformed. A drain electrode of the sensing transistor T2 is connected to areadout line RL, a source electrode is connected to the source electrodeof the switch transistor T1, and a gate electrode is connected to asecond scan line SL2.

Comparing FIG. 5(b) with FIG. 5(a), FIG. 5(b) differs from FIG. 5(a) inthat the drain electrode of the switch transistor T1 is connected to adata line DL, not to the first scan line.

When a selective signal of the first scan line SL1 is supplied to thegate electrode of the switch transistor T1, the switching transistor T1is turned on to charge the contact capacitance C1. When a selectivesignal is applied to the second scan line SL2, the sensing transistor T2is turned on accordingly, to share electric charges charged in thecontact capacitance C1 between the contact capacitance C1 and theparasitic capacitance of the readout line RL.

Specifically, as the contact means approaches the contact sensor SNclosely, a greater contact capacitance C1 is formed between the contactmeans and the contact sensor SN. As the contact means retreats away fromthe contact sensor SN, the contact capacitance C1 is reduced in size.

Thereafter, a signal voltage of the readout line RL is delivered to aseparate IC chip, and the screen contact, contact area, and the like forthe pixel may be identified through the delivered signal voltage. Inother words, the readout line RL senses, as a voltage, a signalcorresponding to an amount of electric charge charged in the contactsensor SN, and the contact and condition thereof can be identifiedthrough the magnitude of the thus-sensed voltage.

According to a manner illustrated in FIG. 5, electric charges stored inthe contact capacitance C1 are delivered to the readout line RL throughthe sensing transistor T2, and parasitic capacitance is to be present inthe contact sensor SN by the circuit configurations on the periphery ofthe contact capacitance C1, the sensing transistor T2, and the readoutline RL, or the correlation with other constituent elements.Accordingly, the contact sensor SN senses a voltage through electriccharges sharing between the contact capacitance C1 and the parasitecapacitance of the readout line RL. Thus, the parasite capacity of thereadout line RL is relatively greater than the contact capacitance C1,which leads to a very low voltage to be sensed.

FIG. 6 is a circuit diagram illustrating the configuration of acapacitive contact sensor applicable for a display apparatus accordingto an embodiment of the present invention.

Referring to FIG. 6, the contact sensor SN according to an embodiment ofthe present invention is included in at least a part of a unit pixelformed in the sensor array layer 300 explained in connection with FIG.2.

Each contact sensor SN may include a pixel electrode and threetransistors. The three transistors may be a reset transistor T1, anamplifying transistor T2, and a detecting transistor T3.

Each transistor T1 to T3 may be implemented as a silicon transistorincluding hydrogenated amorphous silicon (a-Si:H), poly silicon(Poly-Si), oxide transistor, etc., or an organic compound transistorincluding an organic thin film transistor, etc., forming a channel areawith an organic substance. Each transistor T1 to T3 may be implementedas a thin film transistor having coplanar, staggered, inverted coplanar,or inverted staggered structure.

Each transistor T1 to T3 may be formed of a transparent thin filmtransistor (TTFT). A transparent thin film transistor has the propertyof passing the wavelength in the area of visible light. Accordingly, incombination with a display apparatus, visibility can be obtained.

According to an embodiment, each transistor T1 to T3 may be arranged soas not to overlap a unit color pixel in the color filter layer 240, andthe pixel electrode may be arranged to overlap at least a part of theunit color pixel. According to an embodiment, when each transistor T1 toT3 is implemented as a transparent thin film transistor, the transistorsmay be formed to overlap the color pixel.

The reset transistor T1 resets, to a constant level, residual electriccharges of the pixel electrode connected to the amplifying transistorT2, when a signal of the scan line SLn is applied.

The gate electrode of the reset transistor T1 may be connected to thescan line SLn, the source electrode may be connected to the power inputterminal Vdd, and the drain electrode may be connected to the pixelelectrode.

The amplifying transistor T2 serves as an amplifier receiving from thegate electrode a voltage V1 at the contact capacitance C1 generatedbetween the contact means and the pixel electrode (sensing electrode)and delivering, as a current signal, the amount of voltage change to thedetecting transistor T3.

The gate electrode of the amplifying transistor T2 may be connected tothe pixel electrode (sensing electrode), the source electrode may beconnected to the power input terminal Vdd, and the drain electrode maybe connected to the drain electrode of the detecting transistor T3.

The detecting transistor T3 selectively passes a current flowing in theamplifying transistor T2 to the readout line RL. The detectingtransistor T3 passes a current flowing in the amplifying transistor T2to the readout line RL, by a selective signal received from a scan lineSLn+1 which is applied to the gate electrode.

The gate electrode of the detecting transistor T3 may be connected tothe scan line SLn+1, the drain electrode may be connected to the drainelectrode of the amplifying transistor T2, and the source electrode maybe connected to the readout line RL.

According to an embodiment, an opening may be formed at the center ofpixel electrodes included in the contact sensor SN, and each transistorT1 to T3 may be arranged around the electrode edges. Specifically, apixel electrode of a transparent material for generating the contactcapacitance C1 by contact with the contact means may be designed to bearranged at the center of the unit pixel. Each transistor T1 to T3 maybe arranged on the periphery of the location where the pixel electrodeis generated. For example, each transistor T1 to T3 may be arranged inan area not overlapping the electrode edges or color pixels in order toobtain display visibility.

FIGS. 7, 8, and 9 are circuit diagrams illustrating the configurationsof capacitive contact sensors according to embodiments of the presentinvention.

Referring to FIG. 7, the configuration of the contact sensor SNillustrated in FIG. 6 may be changed only in the connection of the resettransistor T1. Specifically, the source electrode of the resettransistor T1 may be connected to the gate electrode, not to the powerinput terminal Vdd. Accordingly, when a selective signal is applied tothe gate electrode from the scan line SLn, the same selective signal isalso applied to the source electrode. Thus, a separate power inputterminal may not be needed in driving the contact sensor SN.

Referring to FIG. 8, the configuration of the contact sensor SNillustrated in FIG. 7 may be changed only in the connection of the resettransistor T1. In the circuit diagram of FIG. 7, the source electrodeand the gate electrode of the reset transistor T1 are connected togetherto the scan line SLn. However, in the circuit diagram of FIG. 8, thesource electrode and the gate electrode of the reset transistor T1 maybe connected together to the power input terminal Vdd.

The above circuit configuration of the contact sensor SN can reduce thenumber of scan lines SLn required for driving each contact sensor. Whenviewed as a whole, the number of scan lines SLn is reduced by one, butas the number of scan lines required for driving each contact sensor SNis reduced from two to one, the operation of a scan driver may besimplified.

Referring to FIG. 9, in the circuit configuration of the contact sensorSN disclosed in the present invention, the contact sensor SN may bedriven only with the scan line SLn, by removing the power input terminalVdd.

Specifically, the source electrode of the amplifying transistor T2 mayreceive a voltage input from the scan line SLn, instead of power inputterminal Vdd, for operation. To this end, a scan driver may be driven todeliver a signal at an operation timing of the amplifying transistor T2.

As such, the removal of the power input terminal Vdd may simplify thecircuit configuration of the contact sensor SN.

FIG. 10 is a timing diagram for explaining the operation of a contactsensor according to an embodiment of the present invention.

Referring to FIGS. 6, 7, 8, 9, and 10, the operation of the contactsensor SN according to an embodiment of the present invention isdescribed as follows.

In FIG. 10, SLn and SLn+1 are indicative of signals supplied to the scanlines SLn and SLn+1, respectively, and should be construed that aselective signal is supplied to the scan lines SLn and SLn+1, during ahigh period. A specific contact sensor SN is selected by the applicationof selective signal, and the signal is output from another contactsensor SN which is connected to the N-1th scan line, when the selectivesignal is applied to the Nth scan line. Hereinafter, “SL” is used torefer to a scan line signal. Also, RL Reset refers to a signal forresetting the readout line RL, and a reset signal is supplied in a highperiod, to reset the readout line RL.

Meanwhile, V1 is indicative of potential of the pixel electrode (sensingelectrode) which is connected to the gate electrode of the amplifyingtransistor T2, i.e., potential by electric charges charged in thecontact capacitance C1 generated between the contact means and the pixelelectrode (sensing electrode). RL is indicative of an amount of currentdetected in the readout line RL which is connected to the sourceelectrode of the detecting transistor T3.

In the timing diagram of V1 and RL, the voltage V1 according to theamount of electric charge charged in the contact capacitance C1 and thecurrent of the readout line RL vary depending on whether a ridge or avalley touches the pixel electrode of the contact sensor SN.

First, a case is described where no contact means contacts the contactsensor SN. As no contact means is present, no contact capacitance C1formed between the pixel electrode and the contact means is present.

When the scan line signal SLn connected to the gate electrode of thereset transistor T1 is converted into a high level, the reset transistorT1 is turned on, and a constant amount of electric charges is charged inthe pixel electrode which is connected to the drain electrode of thereset transistor T1 through a voltage input through the power inputterminal Vdd which is connected to the source electrode of the resettransistor T1. Accordingly, the voltage V1 rises.

The source electrode of the amplifying transistor T2 is also connectedto the power input terminal Vdd, to receive an input voltage. However,the correlation between the gate voltage V1 and the source electrode ofthe amplifying transistor T2 is designed not to exceed a thresholdvoltage of the amplifying transistor T2, in a state where the valley offingerprint contacts the contact sensor SN and thus the contactcapacitance C1 is small. Accordingly, no current is detected in thereadout line RL, as no current is present passing from the drainelectrode of the amplifying transistor T2 to the detecting transistor T3(S2 period).

Next, a case where the valley of fingerprint contacts the contact sensorSN, and a case where the ridge contacts the contact sensor SN aredescribed. As the valley or ridge of fingerprint contacts the contactsensor SN, the contact capacitance C1 is formed between the contactmeans and the pixel electrode in the contact sensor SN. Here, differentsizes of contact capacitance C1 are generated for each case where thevalley and the ridge contact the pixel electrode.

As a selective signal is applied in S2 period to the scan line SLn whichis connected to the gate electrode of the reset transistor T1, the resettransistor T1 is turned on and the signal from the power input terminalVdd is delivered through the drain electrode of the reset transistor T1.Thereby, the contact capacitance C1 is charged.

The magnitude of voltage V1 charged in the contact capacitance C1 variesdepending on the size of generated contact capacitance C1. The size ofcontact capacitance C1 is smaller when the valley of fingerprintcontacts the contact sensor SN than when the ridge of fingerprintcontacts the contact sensor SN, based on a distance between the pixelelectrode and the valley or ridge of fingerprint.

The case where the valley of fingerprint contacts the pixel electrode isdescribed first. When a high signal is applied to the first scan lineSLn (S2), the voltage V1 of the contact capacitance C1 increases by thecurrent flowing from the source electrode to the drain electrode of thereset transistor T1. Then, when the high signal is applied to the secondscan line SLn+1 (S4), as the detecting transistor T3 is turned on, thepotential at the source electrode of the amplifying transistor T2 isdown to 0. Accordingly, the voltage V1 of the contact capacitance C1decreases due to the coupling by parasite capacitance formed between thegate and the source of the amplifying transistor T2. Also, as the highsignal of the second scan line SLn+1 is applied to the gate electrode ofthe detecting transistor T3 (S4), the detecting transistor T3 is turnedon. When the detecting transistor T3 is turned on, the current flowingfrom the drain electrode of the amplifying transistor T2 flows to thesource electrode of the detecting transistor T3 through the drainelectrode, and finally to the readout line RL. In this case, as thevoltage V1 of the contact capacitance C1 is low, the current flowing tothe readout line RL may be smaller than the case where the ridgecontacts the pixel electrode.

The case where the ridge of fingerprint contacts the pixel electrode isdescribed. When a high signal is applied to the first scan line SLn(S2), the voltage V1 of the contact capacitance C1 increases. Here, asthe contact capacitance C1 is relatively greater than the case where thevalley contacts the pixel electrode. Accordingly, no coupling occurs byparasite capacitance formed between the gate and the source of theamplifying transistor T2. Thus, the voltage V1 of the contactcapacitance C1 may remain constantly. Thereafter, when the high signalis applied to the second scan line SLn+1 (S4), the detecting transistorT3 is turned on, and the current flowing from the drain electrode of theamplifying transistor T2 flows to the drain electrode of the detectingtransistor T3 through the source electrode. Then, the current isdetected at the readout line RL. In this case, as no coupling occurs byparasite capacitance, the voltage at the gate electrode of theamplifying transistor T2 remains constantly. Accordingly, a greateramount of current flows compared with the case where the valley contactsthe pixel electrode.

Thereafter, whether the ridge or valley of fingerprint contacts thepixel electrode, the contact area, and the like can be determined basedon the variation pattern of the magnitude of current detected by thereadout line RL.

As such, according to an embodiment of the present invention, when asignal is applied to the scan line, the reset transistor T1 resets thecircuit. Thus, a separate reset line is not necessary. According to thepresent invention, the circuit configuration can be simplified as nowiring other than the scan line is necessary. Also, when a selectivesignal is applied to the scan line which is connected to the gateelectrode of the detecting transistor T3, a single scan line can detecta signal in the readout line RL included in one contact sensor SN andcontrol the operation of the reset transistor T1 included in anothercontact sensor SN, at the same time, as the gate electrode of the resettransistor T1 in another contact sensor SN is also connected to the scanline.

According to an embodiment of the present invention, the amplifyingtransistor T2 operates according to the variation of the contactcapacitance C1. Accordingly, the disadvantage that a signal detected ina charge sharing circuit becomes low can be improved.

Also, according to an embodiment of the present invention, a transparentthin film transistor and transparent electrodes are used, and an openingis formed at the center of the unit pixel. Accordingly, the apertureratio of the display apparatus can increase.

FIG. 11 is a plan illustrating a contact sensor SN according to anembodiment of the present invention.

Referring to FIGS. 6 and 11, the reset transistor T1 corresponds toReset TR illustrated at the top left side of FIG. 11, the amplifyingtransistor T2 corresponds to Amplification TR (Amp TR) at the bottomleft side, and the detecting transistor T3 corresponds to Detection TR(Read TR) at the bottom right side.

The gate electrode RG of the reset transistor T1 may be connected to thescan line SLn, the source electrode RS may be connected to the powerinput terminal Vdd, and the drain electrode RD may be connected to thepixel electrode (sensing electrode).

The gate electrode AG of the amplifying transistor T2 may be connectedto the pixel electrode (sensing electrode) through a contactor Con, thesource electrode AS may be connected to the power input terminal Vdd,and the drain electrode AD may be connected to the source electrode RSof the detecting transistor T3.

The gate electrode RG of the detecting transistor T3 may be connected tothe scan line SLn+1, the source electrode RS may be connected to thedrain electrode AD of the amplifying transistor T2, and the drainelectrode RD may be connected to the readout line RL.

According to an embodiment, when each transistor T1 to T3 is implementedas an oxide transistor, the properties of the oxide may vary dependingon incident light. Accordingly, the contact sensor SN may furtherinclude a shield electrode. The shield electrode may be arranged tooverlap each transistor T1 to T3 as shown in a blue diagonal line areain FIG. 11, to block out light from outside.

Here, the pixel electrode receives the voltage V1 at the contactcapacitance C1 generated between the contact means and the pixelelectrode (sensing electrode) through the gate electrode AG of theamplifying transistor T2, and delivers a current signal with a magnitudewhich is proportional to the change amount of the voltage V1.

However, the contact capacitance C1 increases in proportion to thecontact area between the finger and the pixel electrode. Accordingly, inorder to implement the pixel electrode (sensing electrode) with eachtransistor T1 to T3 on the same plane, as illustrated in an embodimentof FIG. 11, the contact sensor SN may be implemented to minimize thearea each transistor T1 to T3 occupies and maximize the area the pixelelectrode occupies.

According an embodiment, when light transmission of at least oneelectrode material of the source electrode, the drain electrode, or thegate electrode for implementing each transistor T1 to T3 is low, eachtransistor T1 to T3 may be implemented in an area not overlapping colorpixels R, G, B, as illustrated in FIG. 3, and the pixel electrode may beimplemented in an area overlapping color pixels. In this case,fingerprint image scanning is possible, while not disturbing visibilityof the display.

FIG. 12 is a plan view illustrating a sensor array layer 400 where aplurality of contact sensors are arranged, according to an embodiment ofthe present invention. FIG. 13 is an enlarged plan view illustrating thecontact sensor of a unit pixel illustrated in FIG. 12.

Referring to FIG. 12, the sensor array layer 400 may include a pluralityof contact sensors PA. Each contact sensor PA is connected to one dataline DL1, one readout line RL, and two scan lines SLn and SLn+1. For thesake of convenience in explanation, FIG. 12 illustrates that the sensorarray layer 400 includes a group of contact sensors PA arranged in 5×4.However, the present invention is not limited thereto, and the sensorarray layer 400 may be implemented as an array of M×N.

Specifically, referring to FIG. 13 illustrating an enlarged view of theunit contact sensor PA of FIG. 12, one unit contact sensor PA may beconnected to the data line DL, the readout line RL, and the scan lineSL, and include the reset transistor Reset TR, T1, the amplifyingtransistor Amp TR, T2, the detecting transistor Read TR, T3, and thepixel electrode SE.

In FIG. 13, no shield electrode overlapping each transistor T1 to T3 ispresent, and the whole surface of the unit contact sensor PA may overlapthe pixel electrode SE. In this case, the pixel electrode SE may beconnected to the drain electrode RD of the reset transistor T1 and thegate electrode AG of the amplifying transistor T2 through the contactor.

FIG. 14, FIG. 15, and FIG. 16 are side views illustrating the contactsensors PA of a unit pixel illustrated in FIG. 13 taken along the linesA-A′, B-B′, and C-C′, respectively.

Referring to FIGS. 14, 15, and 16, each transistor T1 to T3 forms a gateand a gate insulating layer in the substrate. An active layer is formedin the gate insulating layer, and then the patterning is performedthrough photolithography, to form a source/drain electrode.

Referring to FIG. 14, when viewing the contact sensor from the crosssection taken along the line A-A′, the reset transistor T1 positioned atthe bottom left side may include the source/drain electrode, the gateelectrode, the gate insulating layer G/I, and the active layer. Here,the substrate may be formed of a material such as glass, film, plasticPI, stainless steel, and the like.

The source/drain electrode or the gate electrode of the reset transistorT1 may be implemented with a single substance, such as ITO, IZO, Mo, Al,Cu, Ag, Ti, and the like, or a synthetic substance. The active areabetween the source/drain electrode may be implemented with a-Si:H, lowtemperature poly silicon (LTPS), oxide substance such as indium galliumzinc oxide (IGZO), organic substance, etc. The gate insulating layer G/Imay be implemented with SiO₂, SiN_(X), etc.

The reset transistor T1 may further include an edge stopper. The edgestopper E/S may be implemented with a substance such as SiO₂, SiN_(X),etc. The edge stopper protects the active layer pre-formed by a chemicalsubstance in a photolithography process for preparing the source-drainelectrode, thereby preventing the active area from being damaged.

During a process for preparing the contact sensor PA, a passivationlayer may be formed for making the surface uniform before the pixelelectrode is formed in the reset transistor T1. The passivation layermay be implemented with a transparent substance, such as thin glass,SiO₂, SiN_(X), etc.

As described above in connection with FIG. 13, the drain electrode RD ofthe reset transistor T1 is connected to the pixel electrode SE. Thepixel electrode SE is formed to overlap the whole surface of the unitcontact sensor, as illustrated in FIG. 12 and FIG. 13. Accordingly, thepixel electrode SE may be connected to the drain electrode RD of thereset transistor T1 through the contactor CON formed through an end ofthe passivation layer. The pixel electrode SE may be implemented with asingle substance with light transmission, such as ITO, IZO, Mo, Al, Cu,Ag, Ti, etc., or a synthetic substance.

Referring to FIG. 15, the amplifying transistor T2 positioned at thebottom left side when viewing the contact sensor from the cross sectiontaken along the line B-B′, is formed in the substrate and may includethe source/drain electrode, the gate electrode, the gate insulatinglayer G/I, and the active layer. The detecting transistor T3 at thebottom right side is also formed in the substrate and may include thesource/drain electrode, the gate electrode, the gate insulating layerG/I, and the active layer. Here, the substrate may be formed of amaterial, such as glass, film, plastic PI, stainless steel, and thelike.

The source/drain electrode, the gate electrode, the gate insulatinglayer G/I, and the active layer constituting the amplifying transistorT2 and the detecting transistor T3 are prepared together with a processof constituting the reset transistor. Accordingly, they may be formed ofsubstances the same as those constituting the reset transistor T1.

The amplifying transistor T2 and the detecting transistor T3 may furtherinclude an edge stopper, as in the case of the reset transistor T1described above in connection with FIG. 14. A passivation layer may beformed in the contact sensor PA.

During a process for preparing the contact sensor PA, the gate electrodeAG of the amplifying transistor may be connected to the drain electrodeRD of the reset transistor, and the pixel electrode overlapping thecontact sensor may be connected to the gate electrode of the amplifyingtransistor, as illustrated in FIG. 13 and FIG. 16.

According to an embodiment of the present invention, when scanning thesurface of the contact means with the contact sensor, a transparentelectrode may be implemented with an enlarged size, thereby allowing forvisibility and increasing image sensitivity of a display apparatus.Also, the magnitude of a signal to be detected can increase by using acoupling phenomenon occurring from parasitic capacitance included intransistors and peripheral circuit configurations.

FIG. 17 is a side view illustrating a contact sensor according to anembodiment of the present invention. Hereinafter, for the sake ofconvenience in explanation, a difference from FIG. 14 is mainlydescribed.

Referring to FIG. 17, in a process for preparing each transistor T1 toT3, the gate insulating layer is formed after the gate is formed in thesubstrate. The source/drain electrode may be patterned to be formedthrough photolithography after the active layer is formed in the gateinsulating layer. Here, in order to protect the active layer, an edgestopper area may be further formed before the source/drain electrode ispatterned.

Unlike FIG. 14, the pixel electrode may be formed opposite the substratewhere the transistors are formed. Here, the pixel electrode may beconnected to the drain electrode of the reset transistor T1 and the gateelectrode of the amplifying transistor T2 by a via formed through an endof the substrate. Also, the contact sensor may further include apassivation layer, a protective layer, in the pixel electrode, toprevent the pixel electrode from being damaged by contact of the contactmeans. The passivation layer may include a transparent material, such asthin glass, ultra-thin glass, SiO₂, SiN_(X), etc.

FIG. 18 is a plan view illustrating a sensor array layer where aplurality of contact sensors are arranged, according to an embodiment ofthe present invention. FIG. 19 is an enlarged plan view illustrating thecontact sensor of a unit pixel illustrated in FIG. 18.

Referring to FIG. 18, the sensor array layer may include a plurality ofcontact sensors PB. Unlike the embodiment described above in connectionwith FIG. 12, the contact sensors PB may be symmetrical to otherunidirectional contact sensors.

Specifically, the first contact sensor PB1 to the third contact sensorPB3 may be unidirectionally arranged, for example, in parallel in a linedirection. The first contact sensor PB1 may be symmetrical to the secondcontact sensor PB with respect to the readout line RL or the data lineDL. In such a manner, the second contact sensor PB2 and the thirdcontact sensor PB3 may be symmetrical to each other with respect to theside at which the two sensors meet.

Meanwhile, the first contact sensor PB1 to the third contact sensor PB3may not be symmetric to adjacent contact sensors in a column direction,a different direction from the direction in which the contact sensorsare arranged. Referring to FIG. 18, the first contact sensor PB1 may notbe symmetrical to the fourth contact sensor PB4 with respect to the scanline, the side at which the contact sensors meet.

Referring to FIG. 19, a pair of contact sensors unidirectionallyarranged may be symmetrical to each other with respect to the data lineDL. For example, the reset transistor, the amplifying transistor, thedetecting transistor, the pixel electrode, and the signal lines DL, RL,SL may be symmetrical to each other with respect to the readout line RLor the data line DL.

When adjacent contact sensors are arranged to be symmetrical to eachother, separate data lines may be arranged for each contact sensor.However, according to an embodiment, the symmetry reference line may beshared by two adjacent contact sensors. According to such aconfiguration, the number of signal wirings decreases, the apertureratio of the contact sensor to the display unit pixel increases, therebyimproving visibility of the display.

FIG. 20 is a plan view illustrating a contact sensor according to anembodiment of the present invention.

Referring to FIG. 20, the contact sensor may include the resettransistor, the amplifying transistor, the detecting transistor, thepixel electrode SE, and the signal lines DL, RL, SL.

The pixel electrode SE may be positioned on a different plane from thetransistors and connected to the drain electrode of the reset transistorand the gate electrode of the amplifying transistor through thecontactor CON. The pixel electrode is independent from adjacent contactsensors, and may be formed with an area enough to cover all the sizes ofunit contact sensors. Here, the pixel electrode may be implemented witha single substance with light transmission, such as ITO, IZO, Mo, Al,Cu, Ag, Ti, etc., or a synthetic substance.

As described above in connection with FIG. 11 or below, when the sourceelectrodes, the drain electrodes, or the gate electrodes of the resettransistor T1, the amplifying transistor T2, the detecting transistor T3are translucent or opaque, and when the contact sensor overlaps thedisplay unit pixel, the aperture ratio of the display pixel decreases,and thus the display visibility may be lowered.

According to an embodiment of the present invention, even when thesource electrodes, the drain electrodes, or the gate electrodesconstituting at least one of the transistors are translucent or opaque,the transistors T1 to T3 may be arranged in a black matrix where nocolor pixel CF is arranged in the display pixel in the contact sensor.

The black matrix is an area where driving elements for implementing thedisplay are arranged to block light transmission. Accordingly, when thetransistors and the signal wirings of the contact sensor are formed inthe black matrix, the display visibility may not be lowered.

Although the exemplary embodiments of the present disclosure have beendisclosed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the scope and spirit of the presentdisclosure as disclosed in the accompanying claims. Therefore, it shouldbe understood that the forgoing description is by way of example only,and is not intended to limit the present disclosure. For example, eachconstituent explained in singular form may be carried out beingdispersed, and likewise, constituents explained as being dispersed maybe carried out in combined forms.

The scope of the present disclosure is defined by the foregoing claims,and it is intended that the present disclosure covers the modificationsor variations of the present disclosure provided they come within thescope of the appended claims and their equivalents.

EXPLANATION OF REFERENCE NUMERAL

210: First substrate

220: Thin film transistor layer

230: Liquid crystal layer

240: Color filter layer

250: Second substrate

260: Cover window

270: Protective layer

300: Sensor array layer

SN: Contact sensor

SL: Scan line

RL: Readout line

Vdd: Power input terminal

T1: Reset transistor

T2: Amplifying transistor

T3: Detecting transistor

Con: Contactor

SE: Pixel electrode

What is claimed is:
 1. A display apparatus capable of image scanning,the apparatus comprising a contact sensor arranged in each unit pixel,wherein the contact sensor comprises: a pixel electrode forming acontact capacitance by contact with a contact means; a reset transistorwhere a drain electrode is connected to a node where the contactcapacitance is formed, and each of a gate electrode and a sourceelectrode is connected to a first scan line to which a selective signalis applied; an amplifying transistor where a gate electrode is connectedto the drain electrode of the reset transistor, and a source electrodeis connected to a power input terminal; and a detecting transistor wherea drain electrode is connected to the drain electrode of the amplifyingtransistor, a gate electrode is connected to a second scan line to whicha selective signal is applied, and a source electrode is connected to areadout line detecting a current corresponding to the contactcapacitance.
 2. The display apparatus of claim 1, wherein the resettransistor, the amplifying transistor, and the detecting transistor arearranged so as not to overlap a unit color pixel in a color filterlayer, and wherein the pixel electrode is arranged to overlap at least apart of the unit color pixel.
 3. The display apparatus of claim 1,wherein the reset transistor is turned on by the selective signal fromthe first scan line and delivers to the drain electrode a signal fromthe power input terminal applied to the source electrode.
 4. The displayapparatus of claim 1, wherein the amplifying transistor generates acurrent varying depending on a voltage charged in the contactcapacitance and delivers the generated current to the detectingtransistor.
 5. The display apparatus of claim 1, wherein the detectingtransistor is turned on by the selective signal from the second scanline and delivers to the readout line the current generated by theamplifying transistor.
 6. The display apparatus of claim 1, wherein theselective signal applied to the second scan line is applied after theselective signal is applied to the first scan line.
 7. The displayapparatus of claim 1, wherein the reset transistor, the amplifyingtransistor, and the detecting transistor are formed of a transparentthin film transistor and overlap at least a part of the unit color pixelin a color filter layer.
 8. The display apparatus of claim 1,determining whether contact is made to an upper part of the contactsensor and contact condition, based on the current of the readout linedetected after the selective signal is supplied to the first and secondscan lines.
 9. The display apparatus of claim 1, wherein a passivationlayer is formed between the pixel electrode, and the reset transistor,the amplifying transistor and the detecting transistor, and wherein thepixel electrode is connected to the drain electrode of the resettransistor or the gate electrode of the amplifying transistor through acontactor formed through an end of the passivation layer.
 10. Thedisplay apparatus of claim 1, wherein the pixel electrode is arrangedopposite to a substrate in which the reset transistor, the amplifyingtransistor, and the detecting transistor are arranged, and wherein thepixel electrode is connected to the drain electrode of the resettransistor or the gate electrode of the amplifying transistor through avia formed through an end of the substrate.
 11. The display apparatus ofclaim 1, further comprising a data line, wherein at least a part of thereset transistor, the amplifying transistor, the detecting transistor,the pixel electrode, and the signal line constituting each contactsensor of a pair of contact sensors unidirectionally arranged aresymmetrical with respect to the data line or the readout line arrangedbetween the pair of contact sensors.
 12. A display apparatus capable ofimage scanning, the apparatus comprising a sensor array layer includinga contact sensor arranged in each unit pixel and a color filter layerincluding a unit color pixel, wherein the contact sensor comprises: atransparent pixel electrode forming a contact capacitance by contactwith a contact means and arranged to overlap the unit color pixel; areset transistor receiving a selective signal from a first scan line anddelivering an input power signal to the contact capacitance; anamplifying transistor generating a current varying depending on avoltage charged in the contact capacitance; and a detecting transistorreceiving a selective signal from a second scan line and detecting thecurrent to deliver the current to a readout line, wherein the resettransistor, the amplifying transistor, and the detecting transistor arearranged so as not to overlap the unit color pixel.
 13. A method fordriving a display apparatus, the method comprising: charging a contactcapacitance formed between a pixel electrode and a contact means througha reset transistor turned on by receiving a first selective signal;generating a current varying depending on a voltage charged in thecontact capacitance through an amplifying transistor; and detecting thegenerated current through a detecting transistor turned on by receivinga second selective signal, to determine whether contact is made to anupper part of the contact sensor and contact condition.